Estimate your gestational age, trimesters, and due date. Calibrate your screen to visualize the baby's actual physical size at every week.
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Learn how obstetricians calculate milestones and why accuracy varies.
Standard pregnancy calculators estimate due dates using Naegele's Rule. This rule adds 280 days (40 weeks) to the first day of your Last Menstrual Period (LMP). In this calculator, we automatically adjust for cycle length: if your cycle is longer or shorter than the typical 28 days, the formula adds or subtracts the difference to give you a more accurate due date.
Gestational Age measures the pregnancy from the first day of your LMP, which is roughly 2 weeks before conception actually occurs. This is the timeline doctors and midwives use. Fetal Age (or conception age) is the actual age of the developing fetus starting from the day of fertilization. It is typically 2 weeks shorter than gestational age.
An Estimated Due Date is only an estimate—only about 4% of babies are born on their exact due date. Most babies are delivered within two weeks before or after their EDD. The most accurate date is typically determined via a first-trimester ultrasound scan, which measures the embryo's physical length (crown-rump length).
For In Vitro Fertilization (IVF) pregnancies, the date of conception is known precisely because the embryo is fertilized in a lab. If you had a Day 3 embryo transfer, the due date is transfer date + 263 days. If you had a Day 5 embryo transfer (blastocyst), the due date is transfer date + 261 days.
Answers to the most common questions about pregnancy tests and gestational age.
You should take a pregnancy test on or after the first day of your missed period. For the most accurate result, wait at least one week after a missed period. Testing too early can produce a false negative because hCG (the pregnancy hormone) may not yet be at detectable levels. If your cycles are irregular, count at least 21 days after your last unprotected intercourse before testing.
Most home pregnancy tests can detect hCG as early as 10 days after conception, which is typically about 4 days before your expected period. However, the accuracy improves significantly if you wait until the first day of your missed period or later. For the earliest possible detection, use a first-morning urine sample, which contains the highest concentration of hCG.
To calculate how many weeks pregnant you are, count the number of full weeks since the first day of your last menstrual period (LMP). This is how obstetricians determine gestational age. For example, if your LMP was 6 weeks ago, you are 6 weeks pregnant. Our pregnancy calculator can determine your exact gestational age in weeks and days based on your LMP, conception date, or ultrasound date.
How far along you are is determined by your gestational age, measured in weeks from the first day of your last menstrual period (LMP). A full-term pregnancy is approximately 40 weeks, divided into three trimesters: first trimester (weeks 1–12), second trimester (weeks 13–26), and third trimester (weeks 27–40). Use our calculator to enter your LMP or due date to find out exactly how far along you are and which trimester you are currently in.
Our pregnancy calculator is a free, clinical-grade tool designed to help expecting mothers and healthcare enthusiasts estimate key pregnancy milestones with precision. Whether you are trying to determine your due date pregnancy calculator results or track your baby's growth week by week, this tool delivers accurate, instant calculations without requiring any sign-up or personal data submission.
The core function of any pregnancy calculator due date tool is to estimate when your baby is likely to arrive. Our calculator uses Naegele's Rule, the gold-standard obstetric formula, which adds 280 days (40 weeks) to the first day of your Last Menstrual Period (LMP). What sets our due date pregnancy calculator apart is the automatic cycle-length adjustment. If your menstrual cycle is shorter or longer than the standard 28 days, the formula compensates by adding or subtracting the difference, giving you a far more personalized and accurate estimated delivery date.
The LMP pregnancy calculator method is the most widely used approach in clinical settings. By entering the first day of your last menstrual period and your average cycle length, the tool calculates your gestational age in weeks and days, determines your estimated due date, and maps out all three trimesters. This method is preferred by obstetricians because it provides a consistent baseline that aligns with standard prenatal care schedules and ultrasound dating conventions used worldwide.
Our week by week pregnancy calculator goes beyond simple date estimation. It provides a comprehensive timeline of your pregnancy journey, showing exactly where you stand at every stage. From the moment of conception through implantation, the first heartbeat, fetal viability, and full-term readiness, each milestone is dated and contextualized. The pregnancy calculator week by week feature also includes a trimester progression bar so you can visualize how far along you are relative to the full 40-week term.
For families who conceive through assisted reproductive technology, our IVF pregnancy calculator offers specialized calculations. Unlike natural conception, IVF allows precise knowledge of the embryo transfer date. Our tool supports both Day 3 embryo transfers (transfer date + 263 days) and Day 5 blastocyst transfers (transfer date + 261 days), providing an accurate due date that accounts for the exact developmental stage of the transferred embryo. This level of specificity makes it one of the most reliable IVF pregnancy calculator tools available online.
Sometimes you already know your due date and need to work backward. Our pregnancy calculator by due date method allows you to enter your expected delivery date to determine your current gestational age, estimated LMP, and fetal age. This is particularly useful for women who received their due date from a previous ultrasound or healthcare provider and want to track their progress without re-entering earlier data.
What truly distinguishes this week to week pregnancy calculator is the integrated 1:1 baby size visualizer. Using advanced screen calibration technology, the tool renders your baby's actual physical size at every week of pregnancy directly on your screen. From a tiny poppy seed at week 4 to a full-sized newborn at week 40, you can see and compare the real scale of fetal development. The visualizer includes fruit comparisons, crown-to-heel measurements, and estimated fetal weight for each week, making your pregnancy journey tangible and easy to understand.
All calculations run entirely in your browser. No data is transmitted to any server, making this the most private pregnancy calculator available. Whether you use the LMP method, conception date, ultrasound reference, or IVF transfer calculation, your personal health information never leaves your device. The tool is completely free with no hidden fees, no registration walls, and no advertisements cluttering your experience.